Carbon loss from soil accelerating climate change

Research published in Science today found that increased levels of carbon dioxide in the atmosphere cause soil microbes to produce more carbon dioxide, accelerating climate change.Two Northern Arizona University researchers led the study, which challenges previous understanding about how carbon accumulates in soil. Increased levels of CO2 accelerate plant growth, which causes more absorption of CO2 through photosynthesis.Until now, the accepted belief was that carbon is then stored in wood and soil for a long time, slowing climate change. Yet this new research suggests that the extra carbon provides fuel to microorganisms in the soil whose byproducts (such as CO2) are released into the atmosphere, contributing to climate change.”Our findings mean that nature is not as efficient in slowing global warming as we previously thought,” said Kees Jan van Groenigen, research fellow at the Center for Ecosystem Science and Society at NAU and lead author of the study. “By overlooking this effect of increased CO2 on soil microbes, models used by the Intergovernmental Panel on Climate Change may have overestimated the potential of soil to store carbon and mitigate the greenhouse effect.”In order to better understand how soil microbes respond to the changing atmosphere, the study’s authors utilized statistical techniques that compare data to models and test for general patterns across studies. They analyzed published results from 53 different experiments in forests, grasslands and agricultural fields around the world. These experiments all measured how extra CO2 in the atmosphere affects plant growth, microbial production of carbon dioxide, and the total amount of soil carbon at the end of the experiment.”We’ve long thought soils to be a stable, safe place to store carbon, but our results show soil carbon is not as stable as we previously thought,” said Bruce Hungate, director of the Center for Ecosystem Science and Society at NAU and study author. “We should not be complacent about continued subsidies from nature in slowing climate change.”Story Source:The above story is based on materials provided by Northern Arizona University. Note: Materials may be edited for content and length.

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River dredging reduced fish numbers, diversity

June 10, 2013 — Comparing dredged and undredged sections of the Allegheny River, reduced populations of fish and less variety of aquatic life occurred in areas where gravel extraction took place, according to researchers in Penn State’s College of Agricultural Sciences,.The researchers investigated navigation pools 7 and 8 near Kittanning and Templeton and published their results in the journal Freshwater Biology.”Understanding and untangling the complex effects of human activities on aquatic ecosystems present a challenge to ecologists and resource managers,” said lead investigator Jonathan Freedman. “While the physical impacts of dredging have been relatively well studied, less is known about the ecological impacts, particularly on large-river fish populations.”Freedman focused on small, bottom-dwelling fishes such as darters because they have limited movements and specific habitat requirements, making them more susceptible to the effects of dredging. Several of these species — including Tippecanoe, bluebreast, gilt and longhead darters — are listed on Pennsylvania’s endangered and threatened species lists.Freedman, currently a postdoctoral researcher at the Illinois Natural History Survey, received his doctorate in wildlife and fisheries science in 2010 from Penn State. His research was overseen by his co-advisers, Jay Stauffer, Distinguished Professor of Ichthyology, and Bob Carline, adjunct professor emeritus of fisheries and retired leader of the Penn State Cooperative Fish and Wildlife Research Unit.”We found that at dredged sites, with a maximum depth averaging about 12 meters (slightly more than 13 yards) there was lower species richness and diversity, driven by fewer sensitive species, than at undredged sites in the same navigational pools, which had an average maximum depth of about 5 meters (approximately 5.5 yards),” Freedman said.The research found that total catch, species richness and diversity were negatively correlated with depth, while species richness, diversity and proportion of species that need rocky habitats to spawn were lower at dredged than at undredged sites.”Our analysis revealed that taxa, such as darters, were associated predominantly with undredged sites, while generalist species, such as catfish and suckers, were more associated with dredged sites,” Freedman said. The research differed from most prior studies of the effects of dredging on fish, which were conducted in streams and shallow rivers.”Large rivers are complex ecosystems containing unique fish communities that cannot be understood simply by scaling up the findings from lower-order streams and shallow rivers,” Freedman noted.As a result, “the effects of dredging on deeper rivers — where methods such as electroshocking, gill nets and seines are ineffective for sampling the channel — were largely unknown,” he said. “So we developed an electrified benthic trawl to sample bottom fish assemblages at dredged and undredged sites in a deep, gravel-bed river with a long history of dredging.”In-stream removal of substratum affects the physical and flow characteristics of the river as the channel is modified, creating relatively homogenous, deep stretches, Freedman explained. The removal of coarse gravel and cobble increases river depth, and subsequent accumulation of fine sediment and detritus can greatly alter habitat characteristics required by aquatic organisms.Subsequent bank erosion and head-cutting — the erosion of the upstream end of the dredged area– also can result, further homogenizing the aquatic habitat. The result is a loss of critical shallow-water habitats.Habitat structure for invertebrates and fish is lost as gravel and rocks, coarse woody debris and other structure are removed from the river, the researchers found. Increased depth, compounded by water turbidity, reduces light penetration to the river bottom and reduces biomass and diversity of submerged vegetation and algae.As a consequence, flowing water species are displaced by still water species, while generalist and invasive species displace native habitat specialists.”Changes in substratum composition reduce populations of invertebrates living among rocks and burrowing within sediments and terrestrial detritus, thus altering not only invertebrate assemblage composition, but also fish-foraging efficiency and habitat use,” Freedman said.Many fish species depend on structured habitats for protection from predators and as refuge from the current, and some require rocky and gravel habitat in which to spawn. The loss of this habitat, as well as increased sedimentation rates due to dredging, can render habitats unsuitable for reproduction even if adults are able to survive.River dredging causes a sort of regime shift in fish species, concluded Freedman.”Increased turbidity alters fish-foraging ability, while high sedimentation can affect spawning,” he said. …

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Never forget a face? Researchers find women have better memory recall than men

June 4, 2013 — New research from McMaster University suggests women can remember faces better than men, in part because they spend more time studying features without even knowing it, and a technique researchers say can help improve anyone’s memories.The findings help to answer long-standing questions about why some people can remember faces easily while others quickly forget someone they’ve just met.”The way we move our eyes across a new individual’s face affects our ability to recognize that individual later,” explains Jennifer Heisz, a research fellow at the Rotman Institute at Baycrest and newly appointed assistant professor in the Department of Kinesiology at McMaster University.She co-authored the paper with David Shore, psychology professor at McMaster and psychology graduate student Molly Pottruff.”Our findings provide new insights into the potential mechanisms of episodic memory and the differences between the sexes. We discovered that women look more at new faces than men do, which allows them to create a richer and more superior memory,” Heisz says.Eye tracking technology was used to monitor where study participants looked — be it eyes, nose or mouth — while they were shown a series of randomly selected faces on a computer screen. Each face was assigned a name that participants were asked to remember.One group was tested over the course of one day, another group tested over the course of four days.”We found that women fixated on the features far more than men, but this strategy operates completely outside of our awareness. Individuals don’t usually notice where their eyes fixate, so it’s all subconscious.”The implications are exciting, she says, because it means anyone can be taught to scan more and potentially have better memory.”The results open the possibility that changing our eye movement pattern may lead to better memory,” says Shore. “Increased scanning may prove to be a simple strategy to improve face memory in the general population, especially for individuals with memory impairment like older adults.”The complete study, published in the journal Psychological Science, can be found at this link.

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